As safety awareness has increased, the popularity of helmet use to reduce, if not eliminate, the risk and severity of injury due to a fall or impact also has increased. Helmet use has increased most significantly in cycling, skating, boarding and skiing sports. However, helmets are widely used in most contact sports, construction and industrial environments, motor sports, aviation, military operations, and emergency services.
Generally, protective helmets feature a rigid or semi-rigid external shell and a deformable shock-absorbing interior element. The external shell is typically constructed as a unitary piece, molded to roughly conform to the size and shape of at least a portion of a human head. Openings can be provided for ventilation and to enhance visibility and hearing. A helmet is generally designed to provide a level of protection suitable for the intended use, and helmets can thus vary significantly with respect to the type and amount of materials used.
Helmets with one or more articulating (also collapsible or folding) sections have been developed to reduce the amount of storage space required when the helmet is not in use. In articulating helmets, the exterior shell is seamed to form one or more flaps that can be folded relative to a main portion of the helmet, causing any underlying liner to fold as well. Through this arrangement, peripheral portions of the helmet can be folded into a central (or main) volume defined by the helmet, e.g., reducing the overall size by some amount. However, in order to fold a flap relative to the main portion of the helmet, a locking or securing mechanism typically must be released to permit the flap to move relative to the helmet.
Whether they are entirely rigid or include one or more folding peripheral sections, existing helmets provide a unitary, rigid portion that covers the top (or crown) of the head. The degree to which existing helmets provide protection for the sides, front, and back of the head varies primarily based on the intended use. For instance, cycling helmets typically do not cover much of the skull below the top of the ears while football helmets generally protect the entire skull. Nonetheless, the protection provided by each type of helmet generally cannot be modified beyond its original construction.